Advances in solar technology have led to the development of high efficiency multi-junction solar cells comprised of multiple subcells. Each subcell of a multi-junction solar cell is designed to generate the same amount of current as the other subcells under the same lighted conditions to optimize power conversion efficiency. However, the need for the same current from each subcell has led to compromises in the design of the subcells.
Traditionally, the current generated by each subcell was controlled by reducing the subcell voltage. Specifically, the alloy composition of the base semiconductor layer of the subcell was engineered to yield the desired amount of current. For example, lower bandgap alloys have been used in the base semiconductor layer to achieve a higher current output at the expense of a lower output voltage for the subcell.
The power conversion efficiency of a subcell is a function of both the output voltage and the output current. Therefore, current matching the subcells of a solar cell by altering the alloy composition of the base semiconductor layer adversely affects the power conversion efficiency.
Accordingly, those skilled in the art continue with research and development efforts in the field of solar cells.